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Foundation Framework Reference NSDiscardableContent Protocol Reference

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NSDiscardableContent

You implement this protocol when a class’s objects have subcomponents that can be discarded when not being used, thereby giving an application a smaller memory footprint. More...

Inheritance


Not Applicable

Conforms To


Not Applicable

Import Statement


import Foundation @import Foundation;

Availability


Available in OS X v10.6 and later.
  • Returns a Boolean value indicating whether the discardable contents are still available and have been successfully accessed. (required)

    Declaration

    Swift

    func beginContentAccess() -> Bool

    Objective-C

    - (BOOL)beginContentAccess

    Return Value

    YES if the discardable contents are still available and have now been successfully accessed; otherwise, NOfalse.

    Discussion

    Call this method if the object’s memory is needed or is about to be used. This method increments the counter variable, thus protecting the object’s memory from possibly being discarded. The implementing class may decide that this method will try to recreate the contents if they have been discarded and return YES if the re-creation was successful. Implementors of this protocol should raise exceptions if the NSDiscardableContent objects are used when the beginContentAccess method has not been called on them.

    Import Statement

    import Foundation

    Availability

    Available in OS X v10.6 and later.

  • Called if the discardable contents are no longer being accessed. (required)

    Declaration

    Swift

    func endContentAccess()

    Objective-C

    - (void)endContentAccess

    Discussion

    This method decrements the counter variable of the object, which will usually bring the value of the counter variable back down to 0, which allows the discardable contents of the object to be thrown away if necessary.

    Import Statement

    import Foundation

    Availability

    Available in OS X v10.6 and later.

  • Called to discard the contents of the receiver if the value of the accessed counter is 0. (required)

    Declaration

    Swift

    func discardContentIfPossible()

    Objective-C

    - (void)discardContentIfPossible

    Discussion

    This method should only discard the contents of the object if the value of the accessed counter is 0. Otherwise, it should do nothing.

    Import Statement

    import Foundation

    Availability

    Available in OS X v10.6 and later.

  • Returns a Boolean value indicating whether the content has been discarded. (required)

    Declaration

    Swift

    func isContentDiscarded() -> Bool

    Objective-C

    - (BOOL)isContentDiscarded

    Return Value

    YEStrue if the content has been discarded; otherwise, NOfalse.

    Import Statement

    import Foundation

    Availability

    Available in OS X v10.6 and later.